Microstructural analysis of cold drawn CuAlMn shape memory ...
Transcript of Microstructural analysis of cold drawn CuAlMn shape memory ...
Microstructural analysis of cold drawn CuAlMn shapememory alloy wire
Ivanić, Ivana; Kožuh, Stjepan; Pavičić, Nikolina; Čubela, Dijana;Beganović, Omer; Kosec, Borut; Gojić, Mirko
Source / Izvornik: Proceedings book 18th International Foundrymen Conference, 2019, 237 - 246
Conference paper / Rad u zborniku
Publication status / Verzija rada: Published version / Objavljena verzija rada (izdavačev PDF)
Permanent link / Trajna poveznica: https://urn.nsk.hr/urn:nbn:hr:115:904720
Rights / Prava: In copyright
Download date / Datum preuzimanja: 2022-04-14
Repository / Repozitorij:
Repository of Faculty of Metallurgy University of Zagreb - Repository of Faculty of Metallurgy University of Zagreb
University of Zagreb
Faculty of Metallurgy
Sisak, Croatia
University of Ljubljana
Faculty of Natural Sciences and Engineering
Ljubljana, Slovenia
University North
Koprivnica, Croatia
Technical University of Košice
Faculty of Materials, Metallurgy and Recycling
Košice, Slovakia
ELKEM ASA
Oslo, Norway
PROCEEDINGS BOOK
18th
INTERNATIONAL FOUNDRYMEN
CONFERENCE
Coexistence of material science and sustainable
technology in economic growth
Sisak, May 15
th – 17
th, 2019
ORGANIZERS
University of Zagreb Faculty of Metallurgy, Sisak, Croatia
University of Ljubljana Faculty of Natural Sciences and Engineering, Ljubljana, Slovenia
University North, Koprivnica, Croatia
Technical University of Košice Faculty of Materials, Metallurgy and Recycling, Košice, Slovakia
ELKEM ASA, Oslo, Norway
PROCEEDINGS BOOK
18th
INTERNATIONAL FOUNDRYMEN CONFERENCE
Coexistence of material science and sustainable technology in economic growth
EDITORS
Natalija Dolić, Zdenka Zovko Brodarac, Anita Begić Hadžipašić
TECHNICAL EDITOR
Anita Begić Hadžipašić
PUBLISHER
University of Zagreb
Faculty of Metallurgy
Aleja narodnih heroja 3
44000 Sisak
Croatia
InfOmArt Zagreb d.o.o.
Nikole Tesle 10
44000 Sisak
Croatia
ISSUE
200 copies
ISBN
978-953-7082-34-5
-A CIP record is available in computer catalogue of the National and University Library in Zagreb under the
number 001029655.
UNDER THE HIGH AUSPICES
President of Croatia
Kolinda Grabar – Kitarović
UNDER THE PATRONAGE
Ministry of Science and Education of the Republic of Croatia
Ministry of Economy, Entrepreneurship and Crafts of the Republic of Croatia
University of Zagreb
World Foundry Organization (WFO)
Mittel Europäische Giesserei Initiative (MEGI)
Chamber of Commerce of Republic of Croatia
Sisak – Moslavina County
City of Sisak
SPONSORED BY
SILVER SPONSOR
HEMOLAB Ltd, Beograd (RS)
LABTIM ADRIA Ltd, Sesvete (HR)
BRONZE SPONSOR
BENTOPRODUCT Ltd, Šipovo (BA)
BITUS Ltd, Zagreb (HR)
EBERT Ltd, Ljubljana (SI)
FERRO-PREIS Ltd, Čakovec (HR) HAGI GmbH, Pyhra (AT)
HEINRICH WAGNER SINTO MASCHINENFABRIK GmbH, Bad Laasphe (DE)
LABEKO Ltd, Zagreb (HR)
MECAS ESI s.r.o., Plzen (CZ) & TC LIVARSTVO Ltd, Ljubljana (Sl)
TROKUT TEST GROUP Ltd, Zagreb (HR)
MEDIA COVERAGE
IRT 3000
Foundry Lexicon
Foundry Planet
SUPPORTING ASSOCIATION AND COMPANIES
Croatian Foundry Association
Slovenian Foundry Association
ORGANIZING COMMITTEE
Zdenka Zovko Brodarac, president
Anita Begić Hadžipašić
Sandra Brajčinović
Damijan Cerinski
Natalija Dolić
Gordana Gojsević Marić
Martina Hrubovčáková
Franjo Kozina
Stjepan Kožuh
Ladislav Lazić
Jožef Medved
Marin Milković
Primož Mrvar
Tomislav Rupčić
Sanja Šolić
Iveta Vasková
PROGRAM COMMITTEE
Hasan Avdušinović (BA) Srećko Manasijević (RS)
Branko Bauer (HR) Dragan Manasijević (RS)
Anita Begić Hadžipašić (HR) Jožef Medved (SI)
Jaka Burja (SI) Daniel Novoselović (HR)
Lidija Ćurković (HR) Mitja Petrič (SI)
Mile Djurdjević (AT) Bojan Podgornik (SI)
Natalija Dolić (HR) Karlo T. Raić (RS)
Peter Cvahte (SI) Vera Rede (HR)
Regina Fuchs-Godec (SI) Zdravko Schauperl (HR)
Dario Iljkić (HR) Peter Schumacher (AT)
Sebastjan Kastelic (SI) Ljerka Slokar Benić (HR)
Varužan Kervorkijan (SI) Božo Smoljan (HR)
Ivica Kladarić (HR) Tahir Sofilić (HR)
Borut Kosec (SI) Davor Stanić (HR)
Dražan Kozak (HR) Sanja Šolić (HR)
Stjepan Kožuh (HR) Iveta Vaskova (SK)
Zoran Kožuh (HR) Maja Vončina (SI)
Ladislav Lazić (HR) Zdenka Zovko Brodarac (HR)
Martina Lovrenić-Jugović (HR) Irena Žmak (HR)
REVIEW COMMITTEE
Vesna Alar (HR) Ladislav Lazić (HR)
Ljubiša Balanović (RS) Martina Lovrenić-Jugović (HR)
Jakov Baleta (HR) Dragan Manasijević (RS)
Marko Ban (HR) Ivana Marković (RS)
Branko Bauer (HR) Adrijana Milinović (HR)
Anita Begić Hadžipašić (HR) Aleš Nagode (SI)
Mile Djurdjević (AT) Daniel Novoselović (HR)
Natalija Dolić (HR) Vesna Ocelić Bulatović (HR)
Nikša Čatipović (HR) Mitja Petrič (SI)
Vladan Ćosović (RS) Zora Pilić (HR)
Stanisław Gil (PL) Grzegorz Piwowarski (PL)
Vesna Grekulović (RS) Milena Premović (RS)
Tamara Holjevac Grgurić (HR) Žarko Radović (ME)
Dario Iljkić (HR) Ankica Rađenović (HR)
Ivan Ivec (HR) Matija Sakoman (HR)
Miće Jakić (HR) Božo Smoljan (HR)
Ivan Jandrlić (HR) Ivan Stojanović (HR)
Sebastjan Kastelic (SI) Sanja Šolić (HR)
Zvonimir Katančić (HR) Iveta Vasková (SK)
Witold Kazimierz Krajewski (PL) Tatjana Volkov Husović (RS)
Varužan Kevorkijan (SI) Darja Volšak (SI)
Ana Kostov (RS) Maja Vončina (SI)
Stjepan Kožuh (HR) Domagoj Vulin (HR)
Jure Krolo (HR) Zdenka Zovko Brodarac (HR)
Dajana Kučić Grgić (HR) Irena Žmak (HR)
18th
INTERNATIONAL FOUNDRYMEN CONFERENCE
Coexistence of material science and sustainable technology in
economic growth
Sisak, May 15th
-17th
, 2019
http://www.simet.hr/~foundry/
237
MICROSTRUCTURAL ANALYSIS OF COLD DRAWN CuAlMn SHAPE MEMORY
ALLOY WIRE
Ivana Ivanić1*
, Stjepan Kožuh1, Nikolina Pavičić2, Dijana Čubela3
, Omer Beganović4, Borut
Kosec5, Mirko Gojić1
1 University of Zagreb Faculty of Metallurgy, Sisak, Croatia
2 Master degree student at University of Zagreb Faculty of Metallurgy, Sisak, Croatia
3 University of Zenica Faculty of Metallurgy and Technology, Zenica, Bosnia and Herzegovina
4 University of Zenica Metallurgical Institute Kemal Kapetanović, Zenica, Bosnia and Herzegovina
5 University of Ljubljana Faculty of Natural Sciences and Engineering, Ljubljana, Slovenia
Poster presentation
Original scientific paper
Abstract
The Cu-11.9Al-2.5Mn (wt. %) shape memory alloy was produced by vertically continuous casting
technique obtaining bars of 8 mm in diameter which is applicable for plastic deformation. With the
process of hot rolling and forging the 4.80 mm bar was produced. Afterwards, the obtained 4.80 mm
bar was subjected to cold drawing process. After first run and after fourth run of cold drawing
process the wire with diameter of 4.47 mm and 3.22 mm was produced, respectively. Optical
microscopy (OM) and scanning electron microscopy (SEM) equipped with energy dispersive
spectroscopy (EDS) shown the insight in the samples microstructure. The as-cast state sample has
two phase (α+β) microstructure. After cold working process the two-phase (martensite+α)
microstructure appears. As the result of the cold working process it can be noticed a texture inside
the sample depending on cold drawing direction. The microhardness of samples increases as the
wires diameter decreases.
Keywords: CuAlMn wire, shape memory alloy, microstructure, hot working, cold working
*Corresponding author (e-mail address): [email protected]
INTRODUCTION
Cooper based shape memory alloys (SMAs) are very interesting material for industrial
application due to its good shape memory effect (SME), relatively low cost, good
machinability and damping capacity in comparison to the properties that NiTi alloy obtain.
18th
INTERNATIONAL FOUNDRYMEN CONFERENCE
Coexistence of material science and sustainable technology in
economic growth
Sisak, May 15th
-17th
, 2019
http://www.simet.hr/~foundry/
238
Its excellent thermal stability and very high martensite transformation temperature makes
them rapidly become one of the most promising high temperature shape memory alloys
[1,2].
CuZnAl and CuAlNi shape memory alloys have been extensively investigated due to its
previously mentioned properties. However, these shape memory alloys are too brittle for
cold working because of coarse grain structure and high elastic anisotropy [3]. The large
grain size problem can be solved by using grain size refinements (as titanium and boron for
example) or production by rapid solidification techniques. This type of production ensures
shaping and forming procedures easier [4-6]. Mechanical properties improvement,
preferably meaning ductility, can be provided by adding alloying elements and by heat
treatment as well [7].
Addition of manganese to binary CuAl alloy can significantly improve alloys properties by
stabilizing the bcc phase, widening the single β-phase region to lower temperatures and
improving ductility in low Al alloys (less than 18 at. %) [8,9]. The austenitic β-phase arranged
to the lower order system β1 (L21; Cu2AlMn) and martensitic phase stabilization of unstable
β´3 (18R) to stable γ´3 (2H) ratio can be adjusted by quenching and the amount of aluminium
(Al) and manganese (Mn) [10].
The CuAlMn alloys exhibit shape memory effect and superelasticity based on cubic β1 (L21)
to monoclinic β1' (6M) martensitic transformation. The shape memory characteristics
(superelasticity and shape memory effect) of CuAlMn SMAs can be enhanced by the addition
of alloying elements and the application of microstructure control achieved by
thermomechanical treatment. It has been reported that those characteristics strongly
depend on grain size and the development of texture [11]. Some investigations have been
demonstrated that low thermal expansion can be obtained in CuAlMn shape memory alloys
by controlling stress-induced martensitic transformation due to cold-rolling [8,11].
Due to the fact that CuAlMn shape memory alloy possesses significant ductility the aim of
this paper is to produce a ductile CuAlMn shape memory alloy wire for possible industrial
application with favorable microstructural properties by hot/cold plastic deformation
process.
MATERIALS AND METHODS
Copper-based SMA with the nominal composition of Cu-11.9Al-2.5Mn (wt. %) was prepared
in a vacuum induction furnace. The bar of 8 mm in diameter (Figure 1) was obtained and it
was used for hot/cold plastic deformation process to obtain wire. Firstly, the bar was
subjected to hot working process which was performed by a combination of hot rolling and
hot forging. The forging was performed as free forging and forging in a profiled tool (Figure
2). The obtained bar after first run of rolling and forging was presented at Figure 3. The
forging and rolling procedures were performed alternately till the cross section of the bar
was 4.80 mm. Afterwards, the obtained bars were taken to recrystallization annealing at 580
°C for 60 minutes. After annealing, surface of the samples is brushed for elimination of
possible surface defects propagation during cold working process. After first run of cold
18th
INTERNATIONAL FOUNDRYMEN CONFERENCE
Coexistence of material science and sustainable technology in
economic growth
Sisak, May 15th
-17th
, 2019
http://www.simet.hr/~foundry/
239
drawing the wire with diameter of 4.47 mm was obtained. Followed by three more runs the
wire with ø 4.02 mm, 3.61 mm and 3.22 mm was produced. Between last two runs (ø 3.61
mm and 3.22 mm) the recrystallization annealing at 580 °C for 60 minutes was performed.
The exact procedure of plastic deformation process can be seen in Table 1. Samples selected
for investigation were in as-cast state (Figure 1) and after cold working process with
dimensions ø 4.47 mm and ø 3.22 mm (Figure 4), marked bold and underlined in the Table 1.
Insight into samples microstructure was obtained by optical microscopy (OM) equipped with
digital camera and scanning electron microscopy (SEM) along with energy dispersive x-ray
spectroscopy (EDS). The alloys hardness was determined by Vickers method.
Figure 1. Photograph of CuAlMn shape memory alloy bar ø 8 mm after casting
Table 1. Procedure of plastic deformation process on CuAlMn SMA bars
Deformation process Dimensions (mm) Shematic illustration of
crossection
Sample in as-cast state
HOT WORKING PROCESS - hot rolling and forging
Hot rolling (880 – 900 °C)
2 runs 6.10x8.50
Hot forging (880 – 900 °C) in a
profiled tool
Square side length
6.00
Hot rolling (880 – 900 °C)
1 run 4.50x9.50
Hot forging (880 – 900 °C) in a
profiled tool
Square side length
5.20
Hot rolling (880 – 900 °C)
1 run 4.00x8.70
Hot forging (880 – 900 °C) in a
profiled tool
Square side length
4.60
Hot forging (880 – 900 °C) in a
profiled tool
Square side length
4.80
COLD WORKING PROCESS - cold drawing
Cold drawing Ø 4.47
Cold drawing Ø 4.02
Cold drawing Ø 3.61
Annealing at 580 °C/60’
Cold drawing Ø 3.22
18th
INTERNATIONAL FOUNDRYMEN CONFERENCE
Coexistence of material science and sustainable technology in
economic growth
Sisak, May 15th
-17th
, 2019
http://www.simet.hr/~foundry/
240
Figure 2. Schematic illustration of a profiled forging tool
Figure 3. Photograph of CuAlMn shape memory alloy bar after first run of
hot rolling and forging
Figure 4. Photograph of CuAlMn shape memory alloy wire ø 4.47 mm (a) and ø 3.22 mm (b)
RESULTS AND DISCUSSION
By hot and cold plastic deformation process CuAlMn shape memory alloy wire was
successfully produced. The ductility as a useful property of this cooper based shape memory
alloy enables exhibition of better pseudoelasticity and therefore better hot or cold
workability. It has been reported [8-11] that alloying additions play a very significant role in
the properties of Cu-based shape memory alloys and required properties can be achieved by
proper designing/selection of the alloying elements.
18th
INTERNATIONAL FOUNDRYMEN CONFERENCE
Coexistence of material science and sustainable technology in
economic growth
Sisak, May 15th
-17th
, 2019
http://www.simet.hr/~foundry/
241
Figure 5 and 6 shows results of metallographic analysis by OM and SEM method of CuAlMn
selected samples.
Figure 5. Optical micrographs of CuAlMn SMA in as-cast state (a),
after cold drawing: ø 4.47 mm (b), ø 3.22 mm (c)
As can be seen, the CuAlMn as-cast bar has two-phase (α+β) microstructure (Figure 5a and
6a). It is known that in vertical section of phase diagram of Cu-Al-10 at.% Mn the single
phase region is broadened by addition of Mn and + microstructure exists [12]. Grain
structure with α+β phases a prerequisite for martensite formation after quenching. This
clearly indicates that all the alloys have potential to exhibit the shape memory behaviour
[13].
The influence of plastic deformation process can be seen on microstructures at the obtained
ø 4.47 mm and ø 3.22 mm wires after cold working (Figure 5b, 5c, 6b and 6c). In both cases
after cold working process the martensite appears in some places inside the microstructure.
Considering that the β phase exists in the alloy in as-cast state, during plastic deformation
process transforms into the martensite, probably came to appearance of stress-induced
martensite. The stress induced martensite transformation occurs during loading under the
almost constant stress [14].
18th
INTERNATIONAL FOUNDRYMEN CONFERENCE
Coexistence of material science and sustainable technology in
economic growth
Sisak, May 15th
-17th
, 2019
http://www.simet.hr/~foundry/
242
Figure 6. SEM micrographs of CuAlMn SMA in as-cast state (a),
after cold drawing: ø 4.47 mm (b), ø 3.22 mm (c)
Figures 7 and 8 shows SEM micrographs along with the marked positions for EDS analysis of
CuAlMn wire ø 4.47 mm and ø 3.22 mm, respectively. The results of the EDS analysis for cold
drawn wire with diameter ø 4.47 mm show the difference between position 1 which shows
higher amount of aluminum (7.45 wt.%) in comparison to positions 2 and 3 with amount of
aluminum of (5.30 and 5.03 wt. %), Figure 7 and Table 2. Similar composition difference is
noticed for wire with ø 3.22 mm, Figure 8 and Table 3. The difference between positions 1
and 2 has higher amount of aluminum (6.93 and 6.76 wt. %) in comparison to position 3 with
amount of aluminum of (4.92 wt. %). It can be assumed that the aluminum enriched phase
presents α phase. Sutou et al. [2] reported existence of two-phase microstructure
(martensite + ) in Cu-Al-Mn-Ni-Si alloy after heat treatment at 850 °C. Due to the fact that
the samples between the cold drawing runs were heat treated at 580 °C/60 minutes, the
martensite + α microstructure is possible.
18th
INTERNATIONAL FOUNDRYMEN CONFERENCE
Coexistence of material science and sustainable technology in
economic growth
Sisak, May 15th
-17th
, 2019
http://www.simet.hr/~foundry/
243
Figure 7. SEM micrograph of CuAlMn SMA wire ø 4.47 mm
Table 2. Chemical composition of CuAlMn SMA wire ø 4.47 mm positions
marked at the Fig.7, wt. %
Cu Al Mn
Position 1 82.74 7.45 9.81
Position 2 86.27 5.30 8.43
Position 3 86.47 5.03 8.50
Position 4 86.16 5.17 8.68
Figure 8. SEM micrograph of CuAlMn SMA wire ø 3.22 mm
18th
INTERNATIONAL FOUNDRYMEN CONFERENCE
Coexistence of material science and sustainable technology in
economic growth
Sisak, May 15th
-17th
, 2019
http://www.simet.hr/~foundry/
244
Table 3. Chemical composition of CuAlMn SMA wire ø 3.22 mm positions
marked at the Figure 8, wt. %
Cu Al Mn
Position 1 82.66 6.93 10.41
Position 2 83.17 6.76 10.09
Position 3 86.63 4.92 8.45
The hardness values of the investigated samples are given as mean value of three
measurements and the results can be seen at Figure 9. It is obvious that the hardness of the
alloy increases through the process of cold drawing. The hardness of the alloy in as-cast
state was 268 HV 0.05. Increase in alloys hardness is noticed for wire with ø 4.47 mm (318
HV 0.05) and for wire with ø 3.22 mm (341 HV 0.05), respectively.
Figure 9. Hardness of CuAlMn shape memory alloy before and after cold working process
CONCLUSIONS
With hot and cold plastic deformation process it was successfully produced the CuAlMn
shape memory wire with ø 4.47 mm and ø 3.22 mm in diameter from continuously casted ø
8mm CuAlMn shape memory alloy bar. From the results of microstructural characterization
and hardness measurements can be withdrawn following conclusions:
- From the optical and SEM micrographs obtained grain structure with α+β phases is
visible in the as-cast condition of the CuAlMn shape memory alloy. This
18th
INTERNATIONAL FOUNDRYMEN CONFERENCE
Coexistence of material science and sustainable technology in
economic growth
Sisak, May 15th
-17th
, 2019
http://www.simet.hr/~foundry/
245
microstructure is a prerequisite for martensite formation after quenching indicating
that the alloy has potential to exhibit the shape memory behaviour.
- In some places the martensite formation is observed in CuAlMn alloy wires (ø 4.47
mm and ø 3.22 mm) produced by cold drawing process. During hot and cold working
process appear favorable conditions for appearance of stress induced martensite.
- The results of EDS analysis for cold drawn wires with diameter ø 4.47 mm and ø 3.22
mm shows the difference between the positions enriched with aluminum content
indicating the existence of the α phase in the microstructure.
- The hardness of the alloy increases through the process of cold drawing from 268 HV
0.05 in as-cast state to 318 HV 0.05 wire with ø 4.47 mm and 341 HV 0.05 for wire
with ø 3.22 mm.
REFERENCES
[1] Q. Wang, F. Han, C. Cui, S. Bu, L. Bai, Effect of ageing on the reverse martensitic phase
transformation behaviors of a CuAlMn shape memory alloy, Materials Letters 61(2007),
pp. 5185-5187.
[2] Y. Sotou, N. Koeda, T. Omori, R. Kainuma, K. Ishida, Effects of aging on stress-induced
martensitic transformation in ductile Cu-Al-Mn – based shape memory alloys, Acta
Materialia, 57(2009), pp. 5759-5770.
[3] T. Omori, N. Koeda, Y. Sotou, R. Kainuma, K. Ishida, Superplasticity of Cu-Al-Mn-Ni shape
memory alloy, Materials Transactions, 48(2007)11, pp. 2914-2918.
[4] C. E. Sobrero, P. La Roca, A. Roatta, R. E. Bolmaro., J. Malarría, Shape memory properties
of highly textured Cu-Al-Ni-(Ti) alloys, Materials Science and Engineering A, 536(2012),
pp. 207-215.
[5] I. Ivanić, M. Gojić, I. Anžel, S. Kožuh, M. Rimac, O. Beganović, K. Begović, B. Kosec,
Microstructure and properties of casted CuAlNi and CuAlNiMn shape memory alloys,
Proceedings Book 13th
International Foundrymen Conference, (eds. Z. Glavaš, Z. Zovko
Brodarac, N. Dolić), University of Zagreb Faculty of Metallurgy, 2013, Sisak, Croatia, pp.
153-162.
[6] Z. Wang,X. F. Liu, J. X. Xie, Effects of solidification parameters on microstructure and
mechanical properties of continuous columnar-grained Cu-Al-Ni alloy, Progress in
Natural Science: Materials International, 21(2011), pp. 368-374.
[7] U. Sari, T. Kirindi, Effects of deformation on microstructure and mechanical properties of
a Cu-Al-Ni shape memory alloy, Materials Characterization, 59(2008), pp. 920-929.
[8] Y. Sutou, T. Omori, R. Kainuma, K. Ishida, Ductile Cu-Al-Mn based shape memory alloys:
General properties and applications, Materials Science and Technology, 24(2008)8, pp.
896-901.
[9] U. S. Mallik, V. Sampath, Effect of composition and ageing on damping characteristics of
Cu-Al-Mn shape memory alloys, Materials Science Engineering A, 478(2008), pp. 48-55.
18th
INTERNATIONAL FOUNDRYMEN CONFERENCE
Coexistence of material science and sustainable technology in
economic growth
Sisak, May 15th
-17th
, 2019
http://www.simet.hr/~foundry/
246
[10] U. Arlica, H. Zak, B. Weidenfeller, W. Riehemann, Impact of alloy composition and
thermal stabilization on martensitic phase transformation structures in CuAlMn shape
memory alloys, Materials Research, 21(2018), pp. 1-6.
[11] Y. Sutou, T. Omori, J.J. Wang, R. Kainuma, K. Ishida, Characteristics of Cu–Al–Mn-based
shape memory alloys and their applications, Materials Science and Engineering A,
378(2004), pp. 278-282.
[12] Y. Sutou, T. Omori, R. Kainuma, N. Ono, K. Ihida, Enhancement of superelasticity in Cu-
Al-Mn-Ni shape-memory alloys by texture control, Metallurgical and Materials
Transactions A, 33(2002), pp. 2817-2824.
[13] M. Reza Rezvani, A. Shokuhfar, Synthesis and characterization of nano structured Cu-Al-
Mn shape memory alloy by mechanical alloying, Materials Science and Engineering A,
532(2012), pp. 282-286.
[14] H. Sakamoto, Distinction between thermal and stress-induced martensitic
transformations and inhomogeneity in internal stress, Materials Transactions,
43(2002)9, pp. 2249-2255.